Composition for the preparation of sponge products of butyl rubber



been employed-in sponge -products.-

2 United COMPOSITION FOR THE PREPARATION OF SPONGE PRODUCTS OF BUTYLRUBBER Heinz A. Pfisterer, Point Edward, Sarnia, Ontario, and David W;G. "Hay, Corunna; Ontario, Canada, assignors to Polymer*CorporationLimited, Sarnia Ontario, Canada, acorporation of Canada NoDrawing. Application August 11, 1954 I Serial No. 449,215

Claims priority, application .Canada July .23, 1954 p 2 Claims. (Cl. lil-1,5)

Whichis generally isopren'e. Inany event, the iso-ol'efiu will normallyhave 4 to 8 carbon atoms in the straight aliphatic chain and thediolefinwill normally have 4-14 carbon atoms in the straight aliphaticchain.

.Spouge :rubber products may be produced either :from solid rubbers orfrom high solids latices. -In-the manufacture of sponge rubber fromsolids, .a solid blowing or gassing agent is dispersed as uniformly hasp ossible throughout the rubbery polymer alongwith fillers, pigments,vulcanizers, accelerators, antioxidants, retarders and :othercompounding zingredients. The ililowing or n butyl alcohol.

gassing agents are primarily thermally decomposable-to provide a gaseousmaterial. be either of the closed cell or open cell typesdepending onthe properties required in the product. The closed cell type is achievedby causingsome degree ofvulcaniza- I The sponge products may tionjbefore'the material is allowed fully toe tp'and and finishingvulcanization after expansion, whilethe open cell type is prepared'bypermittingthe material toernand prior tovulcanization. The choice ,of.blowing .agents andother compounding ingredients will be .influcnced'bythe nature of the sponge required. Sodium bicarbonate, ammoniumcarbonate, ammonium nitrate and 'many amino compounds are common blowingagents. Fine .particlesize 'sodium .bicarbonatedras been widely ;usedcommercially, particularly for-open cell sponge .where I uniform. cell.size and low density sate vvnt'ntofprima .portance. .Fattyacids have.been conventionallysemp imlov to promote; the decomposition of; the.sodium bicarbonate.

Natural rubber and certain synthetic rubbers, particu larly polymers-of-butadiene-and styrene,'-havegenerally pc s jrr duct produced from-suchstocks-do notpossessgood 'qz one resistanceand, where'thatpropertyisrequired to an -appreciabledegree, abutyl rubber wouldbe,alogicahchoice. 1

Butyl rubber is recognizedfonits exceptionaliozone resistance andagingproperties, yet, where these properties arerequired in sponge products,there PWm-H IiEQ if any use of this material. Theartheretofore .hastbcenunable to produce acceptablebuftyl sponge. The application ofconventional-sponge compounding practices resuits in a sponge -of--poor"deformation recovery due "to cellular tack. "Efforts "to overcome thisdisadvantage have includedthe incorporation 'of blooming agents. Theblooming agents are intended to migrate to the surfaces, including theinternal surfaces, of'the vulcanized rubber compound and render thesurface less tacky. Sulphur,

selenium, tellurium parafiin waxes, 'fattyacid waxes and high boilingaromatic estersihave-been among-theblooming agents recommended.The-amountaofsuch blocming' agent .employed cdeliberately :cxceeds :thetolerance of. the

, States Patent Patented May 6, 1958 polymerfor such material andblooming results. The incorporation of a paratfin oil facilitates itsmigration. While this is a logical approach to the problerm it has notresulted in a product enjoying any appreciable corninercial acceptance.The blooming in many cases detracts from the apearance of the productand in any event does not result in a sponge of sulficient resilience tobe acceptable for-most purposes. a

It :is the objectof the present invention to suggest a butyl rubbercomposition which eliminates or substantially reduces the aforementioneddisadvantages.

According to the present invention, -a combination-for the preparation.of sponge products comprises a 'butyl rubber polymer, a sulphonatedpetroleum product and talc. The talc-used will normally be all of aparticle Size not coarser than 300 mesh, and the talcis preferablywater-ground.

The combination of the sulphonated petroleum product and the talc isfound to. giveto .the final sponge product a surprising resiliency andexcellent deformation recovery.

The sul'phonated petroleum product is preferably used in Zthe form'oftheplasticizer composition marketed by R. T. Vanderbilt 00., Inc, under thename Plastogen and herein designated by that name. Plastogen is composedof 98% selected mineral oil (about C 1.6% phcnated petro um pr us tu h hn pl an 9 y In whatever form it is used, the s ulphonate'd petroleumproduct is preferably incorp in the proportion of 0.4-5.0% 'by weight ofthe pp The talc'is preferably used in the proportion of 60-95% by weightof the polymer. Q

The preparation of the sponge products will pormally be effected withthe use of blowing agents as d: ibe d above; and i-t'has'been 'foundthat sodium bicarbonate l s the most useful of the blowing agents testedwith the present invention. "Sodium bicarbonate is preferahlyused intheproportion of '5"20% by weight of the polymer. As will be-fullyrealized by persons versed in the lapt -a number of other-ingredientswill be used with the present composition, such ingredients-includingfillers, pigmen s, 'vulcanizers, accelerators, anti-oxidants, retardersand er mundiqs in redien s The e latte how :form qp ofthe ntes'en intctiouti' oun dv nta eou t nsei qgniuu i with Pl tqsen the r a ci ,cqmmitiq 'ltnar eted -R.jI.Vanderbil t Co {Inc under the. name Reogen" andherein designated by that name. ,Reogen iscoriiposedjof '8 min ra ai(C12). 1 .15% r o ts petroleum product ('naphthenic) and 5% n;bptyl alche]. The Reogen gives additional plasticising effect. It is founddefinitely disadvantageous, however, to use naphthenic base oil,paraflinic'base oil and ordinary process OilZf-Ol the purpose ofpla-sticising.

In the practice of the -present invention "We'prefer to employ .a butylpolymer in the -Mooney viscosity range of 70.-.80 ML -8. -Moreover, weprefer-it to "be a relativelyfast curing polymer, i. -e., substantially1.6 nioLipercent unsaturation. Polymers possessinglovyerunsaturation maybe used providing' the compoundingrecipeand cure time -are-adjusted-toallow-for the lower rate "ofcure. Polymers ofhigher-un'saturation mayalso be l'llsdajbut lowcr ozone-resis-tance maybe encopn tered' insuchstoclgs. Polymers of' higher orlower-Mooney viscosity may also beemployed, -though the "former may be difii cult'jto process andthelatter will tolerate less plasticizer. The

following table-is indicative of the components yhich have beensuccessfully employed to prepare compositions according to'the presentinvention and'indicative of certain limited ranges. of proportions whichhave: been i found especially useful; :l?arts arezbyweight perLQOpartsof polymer. y Y l i Y The following are examples of therecipesand methods employed in the preparationof sponge. butyl rubberproducts:' r

Example I I Butyl polymer: (70-80 ML 8, 11.6 mol. percentl unsat.) I1100 Colour f j Reogen 10 ZnO Stearic d I 2 Antioxidant 2 Titaniumdinxirle 2 NaHCO, I I Talc (water'ground '300 mesh) 80 Plastogen i I 55Sulphur 2 Captax. I I 1 Tuadsl. 1.5 Tellurac t 1.5

These components were mixedin a Banbury andon an open mill in thecoiiveritionalflmanner, the sulphurand curing aidsflbeingaddedontheimill. Thecornpound was blown and vulcanized in a mold in the'conventional man ner at 307 F. for30 rriinutes f TheYvulcanized'product was a highly resilienfspongepossessingdeformationrer c'overy comparable to spongetproducts prepared fronatural rubber orbutadiene styrene polymers. I I

I I Example ll;

I i Parts Butyl polymer (7080-ML 8,111.6 .mol.,percent 1 I I 100 Colour;I 2 Xy y m c ta H 10.35

Stear ic arid Antioxidant l I I I H a q .2 Titanium t d? f 1 t 1 =10NaHCoT 1. .Talc (water ground .300 mesh) v30 Plastogen Y r 55 Sulphur 1Captax U h h ..1.5 Tenmc H 7:. s

Comp unding and vuleaniza'tiomw "2mm" v Q g 4 Examples III-X Eightdifferent compositions were prepared as described below and spongeproducts produced therefrom in accordance with conventional procedure.Each composition was based on the following general and conventionalformulation, all parts being by weight:

Parts I 3 T LE 1 I Butyl polymer (70-80 ML 8, 1.6 mol. percent Partsunsat.) 100 Colour As-. desired Reogen 5-15 5 Z30 Stearic acid I 2Antioxidant 2 t t I Titanium dioxide. 5-20 Butyl polymer (70-80 ML 8,1.6 mol. percent NaHCO, (approx.) y 1.0 1 I vunsat.) 100 Talc. (300mesh) 709-90 Zinc: oxide 5 Plastogen I 40-65 Stearic avid 2 Sulphur 12.0 Captax I Mercaptobenzothiazole (as sold under the 1 Tuads 1.5 I nameICaptax andyhereinafter so desiga l Tellurac 1.5 .nated) t 1.0- Sulphur2.0 Tetramethylthiuramdisulfide (as sold. under Titanium io I 10.0 thename ofTuads and hereinafter so desig- Powdered organic colour 6.0-

Tellurium diethyldithiocarbamate (as sold under the name of Tellurac andhereinafter so designated) 1.5

To these basic ingredients there were added the further ingredientsspecifiedin Table II below for eachof the eight compositions denoted byExamples Ill-X respectively. A sponge product was prepared from eachcom.-

7 position according to conventional procedureiand the resilience of thesponge produced is indicated in each case.

TABLE II Examples 111. IV V VI VII VIII IX X 33347;, Napthyl Beta Mereatan- 1 33%75 Xylyl ercap n.-. 1 Reogen 5 l0 l0 10 10 10 10 Plastoizen--.I 56 55 55 55 Naphthenie Base p I I Water-Ground Tale 80 80 80 80 FineSoft Clay-.-- 80 Fine CaCOs 80 Sponge Resilience. very very very veryvery very very very t good good good poor poor poor poor poor "Thewater' 'ground'talc was 325 mesh particle size as sold by EasternMagnesia .Talc (30., Burlington, Vermont,

Examples XI-X V Tabl'e 'III demonstrates that bu tyl polymers of lowerMooney viscosity'and higher andlower mol. percent unsaturation m ay alsobe employed. All examples conformed 'to the basic general formulationspecified for ExamplesjIILX and all further incorporated:

Reogen 1O Plastogen I I l v 55 Talc (300 mesh) 80 NaHCO 10 The onlydifierence 'between the four compositions of these examples is' thedifierence in the viscosity and mol.

' unsaturation-of the polymer used as indicated in Table III. Theresiliency of sponge products prepared from each composition described.

TABLE III- Mooney Mol Per- Example Viscosity. cent Un- Resiliency ML 8satura tion --.-s 40-50 1.4 very good.

40-50 1. 8 D0. -80 1. 6 Do. 40:50 2. 25 Do.

substitute for water-ground tale in some of the above examples and theresults were definitely useful as compared with the results achievedfrom prior art methods. The results with nytal talc were not, however,as good as with water-ground talc.

We claim:

l. A composition for the preparation of sponge products said compositioncomprising an elastic copolymer of a major amount of an isoolefin and aminor amount of a diolefin, 5-20% by weight of polymer of sodiumbicarbonate, 0.55.0% by weight of polymer of a mixture of 98% selectedmineral oil containing about 12 carbon atoms, 1.6% sulphonatednaphthenic petroleum product and 0.4% n-butyl alcohol, and 60-95% byweight of polymer of talc which is substantially all of a particle sizenot coarser than 300 mesh.

2. A composition for the preparation of sponge products said compositioncomprising an elastic copolymer of a major amount of an iso-olefin and aminor amount of a diolefin, 5-20% by weight of polymer of sodiumbicarbonate, 0.5-5.0% by weight of polymer of a mixture References Citedin the file of this patent UNITED STATES PATENTS OTHER REFERENCES TheVanderbilt Rubber Handbook, Ninth Ed. (1948),

T. Vanderbilt Co. (New York), page 370.

1. A COMPOSITION FOR THE PREPARATION OF SPONGE PRODUCTS SAID COMPOSITIONCOMPRISING AN ELASTIC COPOLYMER OF A MAJOR AMOUNT OF AN ISOOLEFIN AND AMINOR AMOUNT OF A DIOLEFIN, 5-20% BY WEIGHT OF POLYMER OF SODIUMBICARBONATE, 0.5-5.0% BY WEIGHT OF POLYMER OF A MIXTURE OF 98% SELECTEDMINERAL OIL CONTAINING ABOUT 12 CARBON ATOMS, 1.6% SULPHONATEDNAPHTHENIC PETROLEUM PRODUCT AND 0.4% N-BUTYL ALCOHOL, AND 60-95% BYWEIGHT OF POLYMER OF TALC WHICH IC SUBSTANTIALLY ALL OF A PARTICLE SIZENOT COARSER THAN 300 MESH.